ISAAC ROBERTS
(1829-1904)

Introduction

One of the most crucial techniques in modern astronomy is
long-integration imaging, where weak signals from faint
astronomical objects are collected over a long period of
time to provide images suitable for detailed study.
The problems of guiding an optical telescope to remain pointing
steadily on a particular point on the sky for long-exposure
photography, despite the rotation of the Earth,
were first solved at the end of the 19th century by Isaac Roberts
and A. A. Common. They were the pioneers of a technique which
is at the core of research in astronomy and astrophysics today.

Isaac Roberts was born in 1829 at Y Groes, a village several
miles to the west of the town of Denbigh in northeast Wales.
He spent some of his childhood there, before settling
with his family in Liverpool in northwest England. He worked in
Liverpool as a builder, eventually making a fortune in the
construction industry. Having reached financial security,
he was able to pursue his leisure interests, in particular
astronomy.

Isaac Roberts took up astrophotography, which had already
achieved some success in fields such as the accurate
measurement of the positions of celestial objects. However,
the potential of photography to record faint images invisible
to the eye was largely undeveloped. Roberts pioneered such
long-exposure photography, initially with large lenses on
accurately tracking mountings. He later turned to photography
through telescopes, purchasing a large telescope with a
20-inch mirror built to his own exacting specifications
and carefully designed by him to track astronomical objects
across the sky with unprecedented steadiness.

Roberts succeeded in photographing many star clusters and
nebulae. He revealed unknown details in these nebulae
(which included both interstellar gas clouds and
what we known today to be galaxies). For example,
he was the first person to identify the spiral shape of
the Great Andromeda Nebula, showing it to be the same type
of object as the spiral nebulae (what we know today to be
spiral galaxies, with the Andromeda Nebula the nearest
to our own Galaxy). He found that the Pleiades star cluster
contained extensive nebulosity between the stars: the extent
of this nebulosity was unexpected. Roberts found the Great
Orion Nebula to be much larger than previously thought and
found a complex structure inside the nebula.
He published many of these photographs in the book
A Selection of Photographs of Stars, Star-clusters and
Nebulae, published in two volumes (the first in 1893,
and Volume II in 1899).

The importance of Isaac Roberts's work was recognised
internationally. He was honoured by being being elected
a Fellow of the Royal Society, the highly prestigious
national academy of sciences of Britain. He was awarded
an honorary doctorate in Dublin (though curiously not
by the University of Wales). He received the gold medal
of the Royal Astronomical Society in London. He met the
American astronomer Dorothea Klumpke on an eclipse
expedition and they later married. He died in 1904.
A crater on the Moon has been named Roberts to honour him
(actually it is named after both Isaac Roberts and
Alexander W. Roberts, a South African astronomer, 1857-1938):
it is situated on the Far Side of the Moon, close to the
lunar North Pole.

Although he lived most of his life outside Wales, and carried
out his astronomical work in England (in Birkenhead, Liverpool
and Sussex), he continued to have strong links with his
native country. He therefore commands a very prominent
position in our survey of Welsh astronomers.

Left: The 20-inch and 7-inch
telescopes in Isaac Roberts's observatory. The 20-inch
reflector was used for photography.
This picture was taken from the introduction to the book
A Selection of Photographs of Stars, Star-clusters and
Nebulae, The Universal Press, London, 1893.

Left: Isaac Roberts's home
and observatory, Starfield, at Crowborough in Sussex.
Taken from A Selection of Photographs of Stars, Star-clusters
and Nebulae (1893).

Left: Isaac Roberts's photograph
of the Great Andromeda Nebula, M31, showing the spiral structure.
Taken from A Selection of Photographs of Stars, Star-clusters
and Nebulae, Volume II, The Universal Press, London, 1899.

Left: His photograph of the
Triangulum spiral nebula, M33, now known to be a Local
Group galaxy. From A Selection of
Photographs of Stars, Star-clusters and Nebulae, Volume II
(1899).

Left: His photograph
of the Veil Nebula in Cygnus.
From A Selection of Photographs of Stars, Star-clusters
and Nebulae, Volume II (1899).

Account in Seryddiaeth a Seryddwyr

Silas Evans provided a short biography in
Seryddiaeth a Seryddwyr, pages 276-279, with two
photographs.

"In memory of Isaac Roberts, Fellow of the Royal Society, one of
England's pioneers in the domain of Celestial Photography. Born at
Groes, near Denbigh, January 27, 1829, died at Starfield, Crowboro,
Sussex, July 17, 1904, who spent his whole life in the search after
Truth, and the endeavour to aid the happiness of others. Heaven is
within us. This stone is erected in loving devotion by his widow
Dorethea Roberts née Klumpke."

Ar dalcen arall y garreg ceir :-

"Heaven is within us, and we have the power to dwell in it all
the days of our life in full happiness, or we may decline and make
ourselves miserable with `cibau gweigion ffol.'
Bydded inni `ddewis y rhan dda.'"

This is Rhys Morris's translation of Silas Evans's account:

ISAAC ROBERTS, D.SC., F.R.S., F.R.A.S. (1829-1904). Born in Y Groes,
two miles from Denbigh. I believe he is one of the greatest astronomers,
if not the greatest of all, that Wales has ever produced. Besides
the acknowledgement made above to the Rev. O. J. Owen, I am indebted
also to Mr. Isaac Davies, 41, The Woodlands, Birkenhead, for some
details about Dr. Isaac Roberts. A good history is to be had in
Y Geninen [The Leek] in 1904 by the late Eleazar Roberts,
and again by the same author in the Ywelydd Misol [Monthly
Visitor] for August, 1905. It appears that his parents emigrated to
America when he was a child, but returned shortly to Liverpool. He was
apprenticed to the contractors Messers Johnson, and rose gradually in the
business, and secured much wealth. He cultivated his mind at the
same time, mainly through astronomy. He "observed" from Rock Park
and Maghull, and later built an observatory costing thousands of
pounds in Crowborough, Sussex. Taking photographs of the stars was
his favourite occupation. He published two valuable volumes-
Photos of Stars, Star-clusters and Nebulae [A Selection of
Photographs of Stars, Star-clusters and Nebulae, The Universal Press,
London, 1893, and Volume II in 1899]. His labours have enlarged
astronomical knowledge greatly.
In his later years he received a lot of help from his second wife,
Dorethea Klumpke Roberts, who is herself in the front ranks of astronomers,
and now lives in San Francisco. As proof of his affection for his
country which he loves constantly- he is a Welshman to the tips
of his fingers- he left a princely sum to the Colleges of Cardiff,
Bangor and Liverpool. He died suddenly in 1904 in Crowborough aged 75
years. After cremation his ashes lay there for about five years, after
which he was reburied in Flaybrick Hill Cemetery, in Birkenhead.
His epitaph is notable:-

"In memory of Isaac Roberts, Fellow of the Royal Society, one of
England's pioneers in the domain of Celestial Photography. Born at
Groes, near Denbigh, January 27, 1829, died at Starfield, Crowboro,
Sussex, July 17, 1904, who spent his whole life in the search after
Truth, and the endeavour to aid the happiness of others. Heaven is
within us. This stone is erected in loving devotion by his widow
Dorethea Roberts née Klumpke."

On the other side of the stone is:-

"Heaven is within us, and we have the power to dwell in it all
the days of our life in full happiness, or we may decline and make
ourselves miserable with `cibau gweigion ffol' [foolish empty vessels].
Bydded inni `ddewis y rhan dda.' [May we choose the good part]."

Left: portrait of Isaac Roberts
from page 277 of Seryddiaeth a Seryddwyr

Below: Isaac Roberts's observatory and
home from page 278 of Seryddiaeth a Seryddwyr

Account in the Dictionary of National Biography

A biography appeared in the Dictionary of National Biography,
the extensive multi-volume encyclopaedia
of the lives of people in Britain.
The article was written by the astronomer H. P. Hollis and
appeared in the Second Supplement, Volume III, pages 209-211,
of the Dictionary of National Biography, edited by
Sir Sydney Lee and published by the Oxford University
Press, 1920. It read,

ROBERTS, ISAAC (1829-1904), amateur astronomer, son of William
Roberts, a farmer of Groes, near Denbigh, North Wales, was born
at that place on 27 Jan 1829 ; though in childhood he left
Wales with his family for Liverpool, he retained a knowledge
of Welsh through life. In 1844 he was apprenticed for seven years
to the firm of John Johnson & Son, afterwards Johnson &
Robinson, builders and lime burners, of Liverpool. One of the
partners, Robinson, died in 1855, and Roberts was made manager.
In the next year, the surviving partner died. Roberts, after
winding up the concern, began business for himself in 1859 as a
builder in Liverpool, and being joined in 1862 by
Mr. J. J. Robinson, son of his former master, the firm traded
for a quarter of a century under the name of Roberts &
Robinson, undertaking many large and important contracts in
Liverpool and its neighbourhood. In 1888 Roberts retired with
means to allow him to devote himself to scientific research.
Whilst still occupied in business, very many branches of science
had engaged his attention. Geology was the first subject that
he took up seriously. He became a fellow of the Geological
Society in 1870, and at the British Associaton meeting of
1878 he read a paper on the filtration of water through
triassic sandstone. Between 1882 and 1889 he made an elaborate
series of experiments on the movement of underground water as
affected by barometric and lunar changes. A paper on a
different subject, `the determination of the vertical and
lateral pressures of granular substances,' which appeared
in the `Proceedings of the Royal Society' for 31 Jan. 1884,
embodied the results of elaborate experiemnts made for the
purpose of furnishing data to engineers and builders of
storehouses.

Meanwhile his attention had been turned to astronomical
observation. In 1878 he had a 7-inch refractor by Cooke at his
home at Rock Ferry, Birkenhead, which he used for visual
observation, but a few years later he applied himself with
zeal to the advancing practice of stellar photography.
In 1883, a year after his removal to Kennessee, Maghull, near
Liverpool, he experimented in photographing stars with
rodinary portrait lenses varying in aperture between
three-eighths of an inch and five inches. After consideration
of the results of these experiments and comparisons with the
photograph of the nebula in Orion by Andrew Ainslie Common
(q. v. Suppl. II), he ordered from Grubb of Dublin a 20-inch
silver-on-glass reflector of 100 inches focal length, the
photographs to be taken directly in the focus of the mirror
to obviate any loss of light on a second reflection, and the
photographic telescope to be mounted on the same declination
axis as the 7-inch refractor, one being the counterpoise of the
other (Monthly Notices R.A.S. xlvi. 99).

At the meeting of the Royal Astronomical Society of January
1886, Roberts, who was at the time the president of the
local astronomical society at Liverpool, reported taking
during the past year 200 photographs of stars which might be
measured for position, as well as long exposure photographs
of the Orion nebula, the Andromeda nebula, and the Pleiades.
At the November meeting in the same year he presented a photograph
of the Pleiades taken with his 20-inch reflector with exposure
of three hours, which showed the stars Alcyone, Maia, Merope,
and Electra surrounded by nebulosity extending in streamers and
fleecy masses till it seemed almost to fill the spaces between
the stars and extend far beyond them. The photograph was
accepted as revealing structure about the group never
before seen or suspected. A photograph of the great nebula
in Andromeda presented at the meeting of December 1888,
which suggested that the object is of the spiral type,
evoked considrable interest because it was supposed to illustrate
the main idea of the nebula hypothesis. Photographs of the
great nebula in Orion, presented a few months later, were
equally successful. Roberts persistently urged the superiority
of the reflector over the refracting telescope, a view that
has since received much confirmation. In the early years of
his work Roberts designed an instrument, the pantograver,
an example of which was made for him by Mr. Hilger, for
transferring mechancially the images on a photgraphic negative
to a copper plate, to be used for making reproductions
(Monthly Notices, Nov. 1888).

Roberts attended by invitation the Conference of Astronomers
at Paris in 1887 which initiated the international survey
of the heavens by photography, but took no part in the scheme,
which was entrusted to professional astronomers at national
observatories with instruments of a uniform type. In order
to continue his work on the nebulae and star clusters in a
clearer atmosphere than that of Liverpool, he finally settled
in 1890 at Crowborough Hill, Sussex, in a house appropriately
named Starfield. There Mr. W. S. Franks, an astronomer and skilful
photographer, became his working assistant, and Roberts confined
himself to organisation and supervision. Month by month for
several years he exhibited at the Royal Astronomical Society
splendid photographs of remarkable objects in the sky taken
with his reflector. Two volumes of selections of Roberts's
photographs of stars, star clusters, and nebulae, 125 reproductions
in all, appeared respectively in 1893 and 1899. In 1896, Roberts,
following the example of Professor Barnard in America,
added to the equipment of his observatory cameras with portrait
lenses of different types, in order to compare their photographic
results with those of the reflecting telescope (cf. a discussion
on the relative efficiency of the two methods between Roberts and
Professor Barnard in R.A.S. Monthly Notices, lvi. 372,
lvii. 10, lviii, 392). Between 1896 and 1902 Roberts prepared
photographs of fifty-two regions of the sky called nebulous by
Sir William Herschel, made with his reflector and with a portrait
lens of 5 inches aperture made by Messrs. Cooke of York.
No diffuse nebulosity was shown on forty-eight of these plates,
a result which was not confirmed by Dr. Max Wolf of Heidelberg,
who made special examination of several cases (Monthly
Notices, lxiii. 303). Roberts's report of this research
was presented in November 1902 (Monthly Notices, lxiii. 26).

Roberts joined the Royal Astronomical Society in 1882. In 1890
he was elected a fellow of the Royal Society, and in 1892 the
honorary degree of D.Sc. was conferred on him by Trinity College,
Dublin, on the occasion of its tercentenary. In 1895 the Royal
Astronomical Society awarded the gold medal to Roberts for
his photographs of star clusters and nebulae, the award being
announced and the address being deleivers by Captain
(now Admiral) Abney, the leading authority on photography,
who congratulated him on his `conclusion that a reflector
is better for his purpose than a refractor.' Roberts went
to Vadso, Norway, on the Norse King, to observe the total
solar eclipse of 9 August 1896, but an overcast sky prevented
observations.

Roberts, who was a zealous liberal, interested himself in
legislation affecting education. He was one of the governors
of the University of North Wales [sic.]. He died suddenly
at Crowborough on 17 July 1904, and his cremated remains
were entombed four years later in a stone in Birkenhead
cemetery, Flaybrick Hill, Birkenhead, on 21 July 1908.
After providing for his widow and other relatives, he left
the residue of his large estate for the foundation of
scholarships in the University of Liverpool and the university
colleges of Wales, Bangor and Cardiff.

He married (1) in 1875 Ellen Anne, daughter of Anthony Cartmell;
and (2) in 1901 Dorothea Klumpke of San Francisco, a member
of the staff of the National Observatory, Paris, who had been a
fellow voyager on the Norse King in 1896. He had no children.

A photograph is in the British Museum series of portraits at
South Kensington.

(Proceedings of the Royal Society, vol. lxxv.; Royal
Astronomical Society Monthly Notices, vol. lxvi and as quoted;
private information.)

H.P.H. [H. P. Hollis]

Obituary of Isaac Roberts in the Proceedings of the
Royal Society

An excellent, detailed obituary of Isaac Roberts was published
in the Proceedings of the Royal Society, vol. LXXV, 1905:
Roberts was a Fellow of the Royal Society. The author of
the articles was given as "R.S.B.", almost certainly
Sir Robert Stawell Ball.

ISAAC ROBERTS. 1829-1904

William Roberts, the father of Isaac, was married in 1825.
Like his father before him, William was a farmer, and he lived
at Groesback [sic.], near Denbigh. It was here that Isaac was
born, January 17, 1829. Though Isaac, while yet in his childhood,
ceased to reside in Wales, he retained throughout his life his
knowledge of the Welsh language, which he spoke and wrote
fluently. It may also be mentioned here that all his life Isaac
was passionately attached to music, as well as to science.
No doubt the second purchase he made out of his savings was a
microscope, but the first was a piano. He had an excellent bass
voice, and in after years became an enthusiastic practising
member of the Liverpool Philharmonic Choral Society.

On November 12, 1844, Isaac Roberts was bound as an apprentice for
seven years to the firm of John Johnson & Son, Builders and
Lime Burners in Liverpool - a firm established sixty years
previously, with a reputation for good building and prosperity.
Mr. Peter Robinson (the father of Isaac Roberts' future partner)
had been with that firm for 30 years, and in 1847 was admitted
a partner, so that Roberts completed his apprentice with the
new firm of Johnson and Robinson. From serving an apprenticeship
with freemen, Roberts became a freeman of the City of Liverpool.
He was remarkable for his industry and desire for information,
and was cited as an example for imitation by the other apprentices.
He was by nature a student, and did not care for many of the
usual amusements of young people. His evenings were passed
at the school of the Mechanics' Institute in Liverpool.
For his master, Peter Robinson, Roberts had a deep admiration
and tried to imitate his many excellences.

Peter Robinson died in 1855, and Roberts was then made manager
of the business of the firm. In 1856 the other partner, John Johnson,
died, and Roberts was engaged to wind up the contracts and
affairs of the firm. In 1859 Roberts began business in a small
way as a hard-working builder in Liverpool, and was very
persevering, and in 1862 Mr. J. J. Robinson, son of Peter Robinson,
joined him as partner, and the firm became Roberts & Robinson.
It is to this partner, the lifelong intimate friend of Roberts,
that I am indebted for these particulars.

The first contract of the firm was the construction of the
Birkenhead Water Works, situate on Flaybrick Hill, Cheshire,
and this was followed by an important undertaking for the
Liverpool Gas Company. The contractor for the erection of the
Lime Street Station Hotel, at Liverpool, belonging to the
London and North-Western Railway Company entrusted the
carrying out of the brickwork and mason's work to Messrs. Roberts
& Robinson. After a successful career as builders for a
quarter of a century, the firm gave up business in 1888, and
thus left Isaac Roberts in possession both of the means to
provide himself with the best scientific instruments and the leisure
to devote himself to their employment.

Some years before the name of Dr. Roberts became known to the
scientific world, the present writer remembers hearing the late
Earl of Rosse remark on the many instances he knew of men,
whom after a successful business career as builders,
devoted a well-earned retirement to practical astronomy.
It is interesting to note that yet another builder, of whom
Lord Rosse had never heard, was destined to develop and
carry onwards to an unanticipated importance Lord Rosse's
own brilliant discovery of spiral nebulae.

Though when at business Isaac Roberts worked with unremitting
diligence and pains, he still found time to supplement an
education which, in his earlier years, had been somewhat scanty.
The result was that he became a recognised master of his
craft as a builder. Roberts was indeed, so much esteemed by
his associates that his aid was frequently invoked as
arbitrator in disputes where technical matters in building were
involved.

At the commencement of his scientific work Roberts devoted himself
principally to geology. The first paper he wrote was in 1869 on the
Wells and Water of Liverpool, and in the following year he became
a Fellow of the Royal Geological Society. In 1878 he read a paper
at the British Association on the Filtration of Water through
Triassic Sandstone, and it was in this year that he commenced
his career as a practical astronomer.

As to the astronomical equipment with which Dr. Roberts accomplished
his work, reference may be made to the interesting account
given by Mr. W. S. Franks in "The Observatory," for August, 1904.
Roberts commenced practical observations in 1878 with a
7-inch refractor by Cooke, which was erected at his residence,
26, Rock Park, Rock Ferry - the same home, it may be noted,
which Nathaniel Hawthorne occupied when American Consul at
Liverpool. In 1882 he moved his residence to Kennessee, Maghull,
near Liverpool. In 1883 Roberts tells us that he made experiments
in photographing stars with ordinary portrait lenses, varying
in aperture between 3/8ths of an inch and 5 inches. The most
efficient of these was one of 2 inches aperture by Lerebours
& Secretan, and he used this as a standard for comparison
with the others. The comparisons were made by attaching the
cameras to the declination axis of the 7-inch refractor,
and taking simultaneous photographs of well-known groups of
stars under precisely similar conditions.

But the great step which he made may be given in his own words
("Monthly Notices" of the Royal Astronomical Society, January, 1886):-
"The result of these experiments, and comparison with Mr. Common's
great photograph of the nebula in Orion, was that I gave
Sir Howard Grubb an order to make me a 20-inch silver-on-glass
reflector, with 100 inches focal length, the photographs to be
taken directly in the focus of the mirror, to obviate any loss
of light by a second reflection, the photographic telescope
to be mounted on the same declination axis as the 7-inch
refractor, one being the counterpoise to the other."
In a foot-note he adds that- "To Dr. Huggins is due the
credit for devising this most ingenious, simple and useful mode of
mounting a reflector and refractor side by side; and the skill
of Sir Howard Grubb is well shown in the arrangements of the
instruments to perform the objects intended."

Mr. Franks records that "over a year was spent by Dr. Roberts
in minor alterations and perfecting details before the instrument
could be considered good enough to perform satisfactorily the
work which was expected of it. From that day to this -
with the exception that a Calver mirror was substituted for
the Grubb in 1888 and a 5-inch Cooke camera added in 1895 -
the equipment remains the same as originally planned by
Dr. Roberts, a fact which speaks for itself as to the patient
forethought bestowed upon this pioneer instrument, which
has now become historically famous."

One circumstance, however, it would ill become the present
writer not to record. Before ordering the 20-inch telescope
from Grubb, Dr. Roberts had obtained an 18-inch instrument
from the same maker. The results were so encouraging that he
decided to enlarge the equipment on the same principle
as above mentioned. The 18-inch telescope thus displaced,
presented by Dr. Roberts to the observatory of Dunsink, co. Dublin.

As to the relative merits of reflectors and refractors for
celestial photographic work, there has been much controversy,
and in this controversy Roberts, as might naturally be expected
from his great success, vigorously upheld the claims of the
reflectors. As Mr. Franks tells us, "Roberts was one of the
earliest and most consistent advocates of the merits of the
reflector for celestial photography, and lived to see his
predilection confirmed in quarters where there had previously
been a strong prejudice for refractors. His views on the
relative performance of camera lenses are well known, but it is
not so well known that he had a very perfect star-camera
fixed on the tube of the 20-inch reflector, with which all
objects were photographed in duplicate, during the last nine
years; and it was the unvarying superiority of the reflector
plates that made him so sceptical as to much that was called
nebulosity on camera plates by other observers."

The climatic conditions of Maghull did not admit of as many clear
nights as an enthusiastic astronomer would desire; accordingly
Roberts, after freedom from the cares of business had rendered
a change of residence possible, determined to move his observatory
to some more favoured locality. He took characteristic pains
to make his change effectual. He personally investigated many
sites. He even went out to the West Indies to see whether
he could there obtain the conditions that seemed to him best.
Finally he decided to establish his observatory on Crowborough
Hill, Sussex, and, as the event proved, no choice could have
been more judicious.

To Crowborough the astronomical equipment was transferred
in 1890, and there, with unremitting diligence, the work was
carried on, so that thousands of negatives have been taken
and carefully preserved as the result. Starfield, as his
house at Crowborough was called, was an ideal home for an
astronomer. At an eminence of 800 feet, it commands a superb
view over the surrounding country. The observatory was in
communication with the commodious residence, and situated
in a beautiful garden. To this garden Dr. Roberts devoted
much care and attention. The visitor to Starfield could not
fail to be impressed by the wonderful gallery of astronomical
photographs there displayed. The plates of comets, of star
clusters, and above all, of nebulae, judiciously selected
from the thousands available, formed a magnificent exhibition
on the walls.

The astronomical work of Dr. Roberts at Crowborough was carried out
with systematic thoroughness. The time tables, according to which the
day was passed, gave to each hour its allotted task. Some hours of
the morning and some of the afternoon were always set apart for
astronomical work. In the early years of his career at Maghull
he was himself the capable photographer of the heavens.
At Crowborough he was so fortunate as to secure the skilful
services of Mr. W. S. Franks as his practical photographer,
and it was by the diligence of Mr. Franks, under the incessant
supervision and guidance of Dr. Roberts, that the wonderful
collection of Crowborough photographs has been obtained.

How diligently the work was carried on from year to year will,
perhaps, be best seen by looking at the successive Annual Reports
of the Council of the Royal Astronomical Society. To these
Reports Dr. Roberts contributed each year an account of the
work done in his observatory during the preceding year.
Of these reports there are about twelve. The last but one,
dated February, 1903, gives a list of about seventy nebulae
which had been photographed during 1902. The photographs were
taken with the 20-inch mirror, which had been recently re-silvered,
and the length of exposure was generally 1½ hours. In this year,
as in others, the principal comets which appeared were also
photographed.

The last of these notable lists, dated February, 1904, contains
a magnificent record of work. There are upwards of ninety entries.
The great majority of the objects photographed are nebulae,
as in the former lists, but a good many clusters, or parts of
the milky way, are included, and occasionally some other objects,
such as the famous star (1830) Groombridge, and the comet
of Borelly, in 1903.

In the words of Roberts himself he "has contributed to the
Royal Astronomical Society and to Knowledge,' between the
years 1886 and 1903, upwards of 150 photographs taken with
his 20-inch reflector, each of which showed structural and
other details of objects in the sky, that were previously unknown
to astronomers." The last words make a great claim, but its
complete justice will be admitted.

Much labour was devoted by Dr. Roberts to the design and
construction of an instrument which he called the Pantograver.
The object of this instrument was to transfer, as it were,
the images of stars, both in size and positions, from a perishable
gelatine film to an imperishable record, by engraving them on a
copper plate. But this machine originated in the early years of
Dr. Roberts' astronomical work, and before the time when he had
fortunately decided to devote himself to the photography of nebulae.
It was at first Dr. Roberts' intention to prepare a photographic
chart of the heavens on a scale twice the size of Algilander's,
and with an exposure of 15 minutes for each plate, and several
specimen plates were sent to the Royal Astronomical Society in 1886.
After the international scheme had been formed by the Convention
in Paris for the preparation of the photographic chart of the
heavens on a vast scale, Roberts saw that his energies could
be most effectively employed in some other direction than that of
charting stars, and thus the Pantograver has had but little
relation to his later work. For a description of this machine
reference may be made to his paper `On an instrument for
measuring the positions and magnitudes of stars in photographs,
and for engraving them upon metal plates, with illustration of
the method of using the instrument.' "Monthly Notices,"
vol. xlix., p. 5.

The Gold Medal of the Royal Astronomical Society was awarded to
Dr. Isaac Roberts in 1895 for his photographs of star clusters and
nebulae. The address on the presentation of the medal was delivered
by the President, Sir W. de W. Abney, whose profound acquaintance
with the photographic arts, made the occasion one of exceptional
interest. In this address Sir W. Abney says:-

"The photographs by Common of the Great Nebula in Orion were epoch-making
in astronomical photography, and worthily was the medal bestowed
on him for his classic work, and it is no disparagement of the
labours of the present recipient (Roberts) if one traces in them
the mark of what Common had shown to be possibilities."

Perhaps the most famous of Dr. Roberts' photographs was that
of the great nebula in Andromeda. This plate it was which
first fully illustrated the capabilities of photography
for the representation of nebulae. Even after the lapse of
15 years it may still be doubted whether any more beautiful
representation of any celestial object has ever been produced.
Of this Sir W. Abney said in the address just referred to:-

"In December, 1886, Roberts produced a photograph of the nebula
in Orion with his 20-inch reflector with an exposure of 15 minutes,
and almost exactly 10 years after he produced a photograph of the
same object with an exposure of 81 minutes, and introduced us
to nebulosities in the surrounding parts which were unsuspected
before. . . . A little afterwards he produced his
recently published photograph of the great nebula in Andromeda,
giving an exposure of 4 hours to the plate. In this prolonged
exposure we have an example of a triumph of patience and instrumental
perfection, though these qualities are exhibited in other instances
as well. This beautiful object is depicted with rings of nebulosity
in great perfection, and we can correct the eye observations
which had previously been made upon it. The stars in the field
are beautifully sharp and round, showing that the eye as well
as the instrument had to be employed throughout that long
exposure to correct changes in the position of the star due
to atmospheric refraction, and variation in the rate of
clock-driving."

Notwithstanding all his later successes with the spiral nebulae,
Roberts always considered the Andromeda picture as his most notable
achievement. In the fine portrait of him which was executed shortly
before his death by his wife's sister, the favourite pupil of
Rosa Bonheur, Roberts is represented resting in an armchair,
and holding in his hand one of his memorable photographs.
The plate which he chose was that of the great nebula in
Andromeda, taken 15 years before. With consummate skill the artist
has reproduced in an oil painting much of the delicacy and
beauty which gave that picture its charm.

In 1896 Dr. Roberts was one of the party who went to Vadso in
the steamship "Norse King" to observe the total eclipse of that
year. The eclipse itself was disappointing, but the circumstance
record from the fact that among those on board was Mademoiselle
Dorothea Klumpke Roberts, D.Sc., of Paris Observatory, herself
an earnest and distinguished worker in astronomical science.
The acquaintance thus begun had a happy issue. In 1901 Roberts
married for the second time, and in this union with his
fellow-traveller on the "Norse King" Isaac Roberts found not
only domestic affection, but also the happiness of sympathetic
co-operation in his notable work. His first wife, to whom he had
been married in 1875, was Ellen Anne, daughter of Mr. Anthony Cartmel.

The chief public testimony to the value of Dr Roberts' work is
found in the facts that in 1890 he became a Fellow of the
Royal Society, that in 1892 he received the honorary degree of D.Sc.
from the University of Dublin [Trinity College, Dublin] on the
occasion of its tercentenary, and that, as already mentioned,
he received the gold medal of the Royal Astronomical Society in 1895.
When he left Liverpool for Crowborough he was presented with an address
signed by the Mayor of Liverpool, the leading citizens, and many
scientific men connected with the University College in that
city. In Crowborough he was highly respected for his vigorous
independence of thought. Though he did not come prominently before
the public as a politician, he held exceedingly strong views
on many public questions. He was an enthusiastic Free Trader,
and a sturdy opponent of the recent Education Acts.

His death took place quite suddenly on July 17, 1904.
He had been working at his negatives on the very last day of
his life, only a few days after he attended the funeral of
his old and valued astronomical friend, Captain Noble.

His estate of ?40,000 he bequeathed for the provision of the
annuities to his widow and other relatives, the capital ultimately
to go to the Universities of Liverpool and Wales for the foundation
of scholarships.

Roberts' photographs will gather increased value as time advances.
The changes in the nebulae, if changes there be, can be only certainly
ascertained by the comparison of the photographs separated by long,
perhaps very long intervals of time. The magnificent plates have been
bequeathed by Dr. Roberts to his widow, Dorothea Isaac Roberts.
In her most capable hands astronomers know that nothing will
be omitted which zeal for the advance of astronomy and
affectionate reverence for the memory of the dead can suggest.

The best memorial of Isaac Roberts is to be found in his two
magnificent volumes of "Celestial Photographs," which he generously
distributed widely among astronomers. We conclude with an extract from
the preface to Roberts' first volume in 1893, which he himself quoted
from in the preface to his later volume in 1899. The dignity of the
words illustrates the character of the man as well as the importance
of his work-

"It has been my aim, in publishing the photographs and descriptive
matter contained in the following pages, to place data in the
hands of astronomers for the study of astronomical phenomena,
which have been obtained by the aid of mechanical, manipulative,
and chemical processes of the highest order at present
obtainable, and tat such data should be, as regards the photographs,
free from all personal errors.

"The photographs portray portions of the starry heavens in a form
at all times available for study, and identically as they appear
to an observer aided by a powerful telescope and clear sky for
observing.

"Absent are the atmospheric tremors, the cold observatory,
the interrupting clouds, the straining of the eyes, the numbing
of the limbs, the errors in recording observations, and the
many hardships incurred by our predecessors of glorious
memory in their attempts to see and fathom the illimitable
beyond.

"I commend the observations and the photographs herein to astronomers
and students of the new astronomy."

R.S.B.

Further reading

The following articles about Isaac Roberts have been published
in recent years:

An article about Isaac Roberts by Michael Hoskin in the
Dictionary of Scientific Biography
(edited by C. Gillispie, published by Charles Scribner's Sons, New York).

An article Discovering M31's Spiral Shape by the
distinguished astronomer Gérard de Vaucouleurs appeared
in the Sky and Telescope magazine in December 1987
(pages 595-598). It is centred around the discovery of the
spiral nature of the Great Andromeda Galaxy by Isaac Roberts.

An article Dr Isaac Roberts (1829-1904) and his
observatories by Stephen James appeared in the
Journal of the British Astronomical Association,
vol. 103, pp. 120-122, 1993. A letter by A. F. Edwards
about the mirror of the 20-inch telescope was written
in response to this article, appeared in the
Journal of the British Astronomical Association,
vol. 103, p. 218, 1993.

The Liverpool Astronomical Society has published a
short pamphlet (with four pages of text) called
Isaac Roberts by Stephen Hughes (1994) as part of
its North-west Astronomers series of booklets. It gives a
useful overview of Roberts's scientific work.
(A brief review by D. Wright appeared in
The Observatory magazine, Vol. 115, No. 1126,
p. 153, June 1995.) The booklet can be ordered from the
Liverpool Astronomical Society for
£1.50, plus postage.

The popular magazine Astronomy
Now carried an article One of the First
Astrophotographers about Isaac Roberts, written by
F. White, in a special feature about astronomers of
the Victorian era (Astronomy Now, vol. 11,
pp. 41-53, May 1997).